Saving changes is not permitted. The changes you have made require the following
tables to be dropped and re-created. You have either made changes to a table that
cant be re-created or enabled the option Prevent saving changes that require the
table to be re-created.
SQL Server management studio—> Tools –>Options—> Designers –>Table and database designers –>Uncheck “Prevent saving changes that require table recreation”
Note: Some operations such as alter column will drop and recreate table. Ensure you do not abort SSMS while operation in progress. You might loose the table. I would recommend
script the changes and and run script in query window (or) At least review the script before you save changes using SSMS.